252+ SpA Aegislash-Blade Shadow Ball vs. 252 HP / 252+ SpD Amoonguss: 133-157 (30.7 - 36.3%) -- 56.1% chance to 3HKO after Stealth Rock and Black Sludge recoveryThose sets are uncommon and still somewhat dealt with by Amoonguss. Head Smash Aegislash nearly dies using it on Amoonguss and SD Aegislash loses to Foul Play. In fact Amoonguss beats any Aegislash if it just lives one hit because it's slower and uses Foul Play. On SD Aegislash Iron Head isn't even the better option over Sacred Sword. Anyway, even assuming Amoonguss actually doesn't check the least common set, what would you say is the best switchin to Aegislash then? Mandibuzz also loses to Head Smash as well as the extremely common SubToxic set.
So I'll say it again just as a major point in favor of Amoonguss being bumped at least to A-. Amoonguss is the best as well as the only completely (sans Head Smash) reliable switch-in to the biggest threat in the meta.
252+ Atk Aegislash-Blade Head Smash vs. 252 HP / 0 Def Amoonguss: 267-315 (61.8 - 72.9%) -- guaranteed 2HKO after Stealth Rock and Black Sludge recovery
0- Atk Amoonguss Foul Play vs. 240 HP / 16 Def Aegislash-Shield: 90-106 (28 - 33%) -- 100% chance to 4HKO after Stealth Rock and Leftovers recovery
+2 0- Atk Amoonguss Foul Play vs. 240 HP / 16 Def Aegislash-Shield: 176-208 (54.8 - 64.7%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
0- Atk Amoonguss Foul Play vs. 240 HP / 16 Def Aegislash-Blade: 328-386 (102.1 - 120.2%) -- guaranteed OHKO
He's right. You can cherry tap it with Foul Play after Spore puts it to sleep if it doesn't attack you.
Huh.